1. Field of the Invention
The present invention relates to an automatic faucet, incorporated in a sink or a urinal or such like, which flushes when a person is detected, and more particularly to an automatic faucet in which flushing is controlled by detecting infrared rays.
2. Description of the Related Art
In a washroom sink or an automatic toilet, infrared rays are radiated toward a person, the presence of the person is detected based on how the infrared rays are reflected, and, when the person has been detected, flushing is carried out by controlling a flush valve. In the case of a sink, a sensor is provided near the flush hole and infrared rays are radiated downward like the flow of water to the bottom wall of the sink, so that hands inserted near the tap can be easily detected.
When this radiated light is reflected midway by the hands of a user, the amount of radiated light increases. Using this effect, the presence of the user is detected by comparing the amount of reflection with a reference value, and flushing is carried out accordingly. When the user retracts his hands and the amount of reflection returns to its original amount, this is detected and the flushing stops.
FIG. 7 shows the construction of a conventional automatic faucet which performs this operation. A microcomputer 1 uses the output from a drive circuit 2 to radiate infrared rays from an infrared light transmitter 3 toward the body of a user 4. The reflected light is detected by a light receiver 5, amplified by an amplifier 6, and the microcomputer 1 reads the result of a comparison performed by a comparator 7. Then, a driver 8 opens and closes an electromagnetic valve 9 in compliance with a two-value determination output from the microcomputer 1.
The distance from the sensor to the bottom of the sink varies depending on the dimensions of the sink, and therefore the reference value, which the reflection amount is compared with, needs to be altered. This is achieved by adjusting a variable resistor, connected to the reference input terminal of the comparator 7. The reference value is set higher than the value of the amount of reflected light so that, if the amount of light reflected from the sink gradually increases due to environmental changes, flushing does not happen of its own accord.
The reference value is set based on intuition gained from experience, and is consequently difficult to set appropriately. Moreover, as shown at the symbol VR in FIG. 8, the variable resistor is provided at a position of poor workability which is awkward for a person to reach, such as on the lower side of the washbasin.
Furthermore, when a cup or the like has been placed on the bottom wall of the sink, it may be mistakenly detected as a hand, causing continuous flushing.
To prevent such inconveniences, some automatic faucets have a function whereby, when infrared rays have been detected for longer than a predetermined time, flushing is temporarily stopped, and does not continue until reflection is detected a second time after a predetermined amount of reflected light has disappeared.
However, this function is complex since flushing is not repeated until the cup or the like is removed, requiring that the cup or the like be extracted.
Furthermore, when installing an automatic faucet to an existing washbasin, the washbasin may already be dirty and have poor reflectivity. When the detection distance is set for a washbasin in such a state, the reflectivity of infrared rays will improve if the washbasin is subsequently cleaned. Consequently, the automatic faucet mistakenly detects hands even though no hands are present, and flushes as a result.
On the other hand, there is a problem that, when the reference value of a sink with excellent reflectivity has been set, its range of detection is narrow.
In the case of a urinal, the worker who performs the adjustment must avoid working within positions at which a user will be detected, resulting in poor workability.
In any case, since the operation must be performed manually, there are inevitably inaccurate adjustments, and adjustment takes considerable time to complete.
The present invention has been devised in consideration of the points mentioned above, and aims to provide an automatic faucet, wherein a reference value can be automatically set in accordance with the state of the sink, without requiring further adjustment.
In order to achieve the above objects, the automatic faucet of the present invention comprises a faucet; a sink which receives water from the faucet; a light generator for radiating infrared rays toward the bottom wall of the sink; a light receiver for receiving infrared rays, reflected from the bottom of the sink, and detecting an amount of light thereby received; a flush output portion for comparing the detection output from the light receiver with a reference value, and creating a flush output when the detection output exceeds a predetermined value; and a faucet controller for opening and closing the faucet in correspondence with an output of the flush output portion; the automatic faucet further comprising: command means for generating a command signal to correct the reference value; a detection means for detecting the maximum amount of light, received by the light receiver when a signal has been supplied by the command means; and a reference value correction means for correcting the reference value in the flush output portion, based on the maximum amount of light.